[R-390] Balanced and Unbalanced antenna leads.

[David Wise]

I didn't vet your cable swaps for correctness,
but this sounds like a standard field mod that
was done at some installations, primarily
shipboard IIRC.  Normally, the balanced
antenna jack goes to the primary of the
1st RF transformer while the whip antenna
jack goes to the (tuned) secondary.
If you use a really long whip, the secondary
is pulled so far off that the ANT TRIM control
cannot compensate.  In situations like that,
the mod is done, which connects the whip to
the primary and (not that anyone cares) the
balanced input (which is no longer balanced)
to the secondary.  Now your whip will be
treated as untuned.  You also get a little
more gain due to the transformer stepup.
Basically, it saved them from having to
use an external adaptor.  For home use,
I'd say it's only useful if your antenna
coax ends in a C connector.

73,
Dave Wise

> -----Original Message-----
> From: William Patrick Smith [mailto:smithw@WPI.EDU]
> Sent: Wednesday, April 30, 2003 4:54 PM
> To: r-390@mailman.qth.net
> Subject: [R-390] Balanced and Unbalanced antenna leads.
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> Hi, The r390a that I own had a simple mod done to it, usually=20
> Cable p207
> goes to j107, p206 to j106 and p205 to j105... mine has p205=20
> to j106 and
> p206 to j105... one of the balanced going to the unbalanced-in and the
> unbalanced going to the balanced-in...
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> Schematic Dia fig 5-13 shows the radio with either configuration...
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> Which one is right? At the moment the reciver is basically=20
> deaf from the
> balanced input with the cables either way but hears fine from the
> unbalanced whip input.
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> Thanks
> -Bill KE1GF
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